Between a sender and a receiver exists a datapath (path) over which application data flows (dataflow or flow) between the sender and receiver. Reserving network layer resources for the dataflow provides a quality of service (QoS) to the sender and the receiver for that dataflow. Resource reservation protocols reserve network layer resources for data flows. In an “on-path” resource reservation protocol, such as Resource ReSerVation Protocol (RSVP), Next Step In Signaling (NSIS), and Network Layer Signaling (NLS), protocol messaging or signaling are communicated or otherwise exchanged over the datapath of the dataflow between the sender and receiver. For example, in a Voice Over IP (VoIP) call between a calling party (sender) and a called party (receiver), resource reservation messages or signals (e.g., RSVP PATH and RESV messages) reserving network layer resources for the call are communicated on the same datapath as application data or media data (e.g., Real-Time Transport Protocol (RTP) packets).
A dataflow extends in a downstream direction from a sender to a receiver and may traverse one or more intermediate nodes internetworking the sender and the receiver. Conversely, the dataflow extends in an opposite direction from the receiver to the sender, again traversing any intermediate node internetworking the sender and the receiver. As such, to provide QoS between the sender at one end and the receiver at another end, reserving network layer resources for an end-to-end datapath requires reserving network layer resources not only at the sender and the receiver, but also at intermediate nodes internetworking the sender and the receiver. This is referred to as installing an end-to-end reservation.
Many factors conspire against installing an end-to-end reservation. A sender and a receiver are likely to belong to different administrative domains administrated by different providers. Additionally, it is likely that between the administrative domains, to which the sender and the receiver belong, there are additional or “transit” domains administered by still different providers. As such, a dataflow between the sender and the receiver may flow over a datapath which traverses several administrative domains, each using a different resource reservation protocol that is incompatible with one another, or choose to not have a reservation protocol configured for use within any one of the administrative domains. Thus, interoperability between domains may hinder installing an end-to-end reservation.
Even if all administrative domains, through which a datapath traverses, use the same resource reservation protocol or the resource reservation protocols used are all compatible with one another, it is unlikely a provider would permit or otherwise grant permission to a host or node outside of its administrative domain to reserve network layer resources within its domain. Thus, policy considerations also hinder installing an end-to-end reservation.